Abstract: An apparatus for making pulsed acoustic measurements to determine particle size in a sample (1) such as a colloid. The apparatus includes two electrodes (2) between which an electric voltage is applied to the sample. The voltage is applied in short pulses. The applied voltage generates an acoustic signal, such as a sound wave (5), in the sample which is detected with a transducer (3) after the wave (5) has passed through a delay element (4). The delay element (4) is used to introduce enough of a time delay between the application of the voltage pulse and sound wave (5) reaching the transducer so that the received wave's signal can be isolated from any signal generated in the transducer (3) by the applied voltage. The delay element (4) and the transducer (3) are arranged into a geometry, or, alternatively, the delay element (4) is shaped, so that any reflections of the sound wave (5) from the sidewalls of the delay element (4) are deflected away from the transducer (3).

Abstract: A method and device is disclosed for determining the distribution of charge and size in a colloidal system. The arrangement disclosed is adapted to measure these characteristics in an inhomogeneous colloid. A colloid is subjected to a steady or slowly varying force which moves the particles at a rate that depends on their radius or charge and thereby sets up spatial inhomogeneities in the suspension, and to either a unsteady mechanical force or an unsteady electrical force, and the resulting electrical or acoustic effects sensed. Monitoring these characteristics over time and subsequent calculation allows the determination of charge and size distribution, for each species present.

Abstract: A method for the determination of particle size and electric charge or zeta potential of particles dispersed in a fluid medium. The particle size and charge are determined from measurements of (1) the phase lag between an applied alternating electric field and the resulting particle velocity, and (2) the amplitude of the particle velocity. Also disclosed is the measurement of the interaction of sound waves and electric fields in the fluid medium over a range of frequencies to obtain the particle size and zeta potential.